Steel foil and manufacture



NOV- 2, 1965 E. J. SMITH ETAL 3,214,820

STEEL FOIL AND MANUFACTURE Filed Feb. 8, 1963 2 Sheets-Sheet 1 EDWARD PSPENCER 0 d' N O 0 8' N I 5 5 5 5 5 8 8 g g SHANLEY AND o NHL (sami)sanxoml ATTORNEYS Nov. 2, 1965 Filed Feb. 8, 1965 E. J. SMITH ETAL3,214,820

STEEL FOIL AND MANUFAGTURE 2 Sheets-Sheet 2 MILD STEEL STRIP .003#I T0.065" GAGE IRON ALLDY- LAYER FREE PLATING COLD REDUCING AT LEAST 70%STEEL FOIL .000I" T0 .002" GAGE FIG4 INVENTOR EDWIN J` SMITH EDWARD P.SPENCER United States Patent O Y, 3,214,820 p STEEL FOIL AND MANUFACTUREEdwin J. Smith and Edward P. Spencer, Steubenville,

Ohio, assignors to National Steel Corporation, a corporation of DelawareEnea Feb. s, i963, ser. No. 257,310 l1 Claims. (Cl. 29-18) The presentinvention is concerned with new flat rolled steel product and relatedstrip steel finishing operations.

Production methods for flat rolled steel and the basic stri-p steel`finishing processes and products have lcng been well established andstandardized in the steel industry. Hot rolled products are reduced inhot strip mills to ygages las thin as 0.0449 and then reduced in coldrolling mills to gages as thin as 0.006. In recent strip steel tinishingoperations, further cold reduction has produced thin tinplate gages aslow as .004".

The invention departs from practices of the prior art and includesteachings on products and processes of manufacture which realisticallyestablish steel in the metallic foil art. One object of the invention isthe manufacture of plated steel foil with many industrial and commercialuses which possesses high strength, abrasion resistance and which can bebent and crumpled without breaking. This product is produced by coldrolling plated steel having a starting gage between about .003 inch and.065 inch to reduce the plate steel 70% and higher to a finish gagebetween about .0001 inch and .002 inch.

By way of example, tinplated steel foil below a halfthousandt-h of an-inch has been produced in accordance with the teachings of theinvention without any of the problems developed in thin tin practice. Itis -springy and can be bent repeatedly through substantially 360 withoutcracking or breaking and can be crease folded and opened 4repeatedlywithout cracking or breaking. Coating adherence and coating protection.are excellent. It has high tensile strength, from live to ten timesthat of :aluminum foil of the same gage, is more abrasion-resistant thancommon foils, such as aluminum, yet can 'be torn and cut readily. It hasa smooth, fully plated, bright surface. Tests indicate that itscorrosion resistance exceeds that which would be expected from thethickness of it-s tinplating which can be about two-millionths of aninch.

An object of the invention is lmanufacture of steel base foil ashereinafter described. Part of the invention was the discovery that itwas actually possible to make plated steel foil and, also, theconception of numerous lapplications for a plated steel foil in modifiedland combined forms for packaging, for consumer and engineer-ing uses,and for other industrial uses which have opened the door to manypractical uses `of steel foil in all forms.

In the metallic foil industry, as previously constituted, foil wasdefined as thin metal membrane of less than .006 thickness and wasdistinguished from metal of greater thickness called sheet, strip, orplate. Steel does not remain a pliable membrane up to .006 thickness.Steel of less than .006, say .005, is not foil. For example, .005tinplate and the lighter forty-pound per base box tinplate lareavailable in `the rigid can market for beer, oil, food, etc. Therefore,-in describing the present invention, it becomes necessary to set limitsfor steel foil gages other than those accepted for the common metals `ofthe foil industry. Steel foil, therefore, as referred to herein, isdefined as thin metal membrane of not greater than about .002 thickness.Further, steel foil, especially in a plated condition, is distinguishedfrom other ilat rolled finished steels, such as thin tinplate, by a coldredu-ction after plating of substantially in excess of 50%, e.g. 70% andhigher, without an anneal.

Test standards for steel foil have not been established as yet. It has'become -obvious that testing apparatus and methods, e.g. Rockwell andBrinell hardness, Pittsburgh lock-seam tests, and the like, customarilyused in the steel indust-ry, are not applicable to steel foil. Atpresent, comparative tests with other metal foils and steel productsmust lbe used. For example, steel 4foil has a tensile strength five toten times greater than that of aluminum foil of the sa-me gage. Theabrasion resistance of steel, again partially dependent upon theplating, far exceeds that of aluminum, making tinpla-ted steel foil, forexample, far superior to aluminum foil for many industrial uses.

It has been found that the springiness and other rnechanical propertiespeculiar to steel in foil form can be varied by the rolling procedure.For example, tinplate sto-ck reducing in .a single pass to foil gage isnot as springy as tinplate stock reduced a total of 90% by col-d rollingpasses of from 20% to 30% reduction .per pass. -Bot'h products have asimilar appearance and both, in the as rolled condition, would beconsidered full har but the springiness and -other special mechanicalproperties peculiar to steel foil would differ.

Full hard, as previously known in the steel industry, may requirefurther definition when applied to steel foils. Undoubtedly, both of theabove 90% cold reduced samples have the strength and other propertiesassociated with full hard as known in the steel industry but neitherexhibits the poor bending qualities or brittleness ordinarily associatedwith full-hard steel which has been cold reduced 90%. Even when reducedt-o foil gages in a single pass of greater than 90% reduction, steelfoil does not exhibit any of the brittleness expected. It can be bentand folded repeatedly without cracking. Some of the mechanicalproperties of foil are influenced considerably by the method and speed`of reduction. It is believed that the heat produced during rolling hasa greater effect, often instantaneously, at the thin gages involved thanwould be the case with -conventional steel strip.

Many desirable properties of plated steel foil materialize because ofproper practice in the manufacture of plated steel foil. Again usingtinplated steel foil by way of example only, it has been found veryimportant in practice, for purposes of 'avoiding rolling and otherproblems, to metal coat the strip steel in an iron-alloy layer freemanner. Ordinarily, this would involve either electroplating, gasplating, electrophoretic plating, or vapor plating, all herein embracedunder the `term plating; however, some hot ydip experts maintain thatsteel can be hot dip coated without an iron-alloy layer, and to theextent that this is possible, such a product could be used, especiallywith the heavier gage steel foils.

The .present invention includes the discovery that a matte-finishtinplate is preferred as starting stock for tinplate foil. Practice withmatte-finish tinplate substantiates the aforementioned teachings onavoidance of an alloy layer between the coating metal and the basemetal. n flow brightening of electroplated tinplate, an alloy layer isfor-med. It has been found with .011 tinplate having one pound per basebox of coating that the ill eHects of an alloy layer begin to show up atthicknesses of approximately two to three-thousands of `an inch.Tin-iron alloy crystals protrude through the -coating and grey streaksshow up on the surface of the product at about these thicknesses. Also,tin-iron alloy scale forms on the work rolls. The matte-finish of tin,zinc, and other coating metals is converted to a bright lfinish inrolling to the foil gage-s taught by the present invention.

In rolling plated strip steel to foil gages, work hardening propertiesof the coating metal can be critical.

With fini-shed strip steel currently available and that contemplated bythe invention, reductions greater than 95% will take place withoutintermediate annea'l. It has been found in cold reducing to foil gagesthat the coating metal reduces in proportion to the base metal. Whilethe lsteel Vitself can be cold reduced in the prescribed ranges withoutan anneal, many of the coating metals included in the invention cannotwithstand such cold reduction without an anneal. Therefore, it isnecessary, in some instances, to match the cold reducing properties andthickness of the coating metal to the starting thickness of the steelbase metal. For example, coating metal which will only reduce 60%without an lanneal should be used only with a coated starting stockhaving a thickness gage calling for not more than 60% reduct-ion to thefinished foil. Otherwise, as the maximum permissible reduction withoutanneal is reached, coating metal will come off during contact with thework rolls. On the other hand, with many coating metals, this problemcan be solved by the roll-ing practice. For example, controlling rollinglubricant temperature can add the necesary malleabllity to zinc andsolve many work-hardening `problems of low temperature anneal metals.`Other metal-s `such as tin are found to be self-annealing during coldrolling with or without control of lubricant temperature. Where an an*nealing problem does exist with a coating met-al, selected frequencyinduction heating can usually be readily matched to the needs of aparticular problem because of the precisional control of temperature andheat penetration available. Induction and :other forms of heating, suchas hot oil baths, can also be used for heat treating the steel itselfsince the various effects of heat treatment such as stabilizing, strainrelief, and softening occur readily yand apparently at lowertemperatures when dealing With toil gages.

The coating metal thickness, both starting and iinal, become moreimportant when it is considered that plated steel foil will be reducedto gages as low as one ten-thousandth of an inch (0001"). Thecombinations of plating thickness and -steel base metal thickness gagesavailable in foil form approach infinity when it is considered that thefoil can vary between about .002 and about .0001 and Ialso that theinitial coating weight can vary, with tin for example, from a ashcoating up to several pounds per base box (2117.78 sq. ft.). The scopeof these variations can be co-mprehended from graphical representationssuc'h as those shown in the accompanying drawings, wherein:

FIGURE 1 is a graphical representation of the change in thickness ofstrip steel with percentage cold reductions falling within the scope ofthe present invention;

FIGUR-E 2 is a graphical representation of the change in thickness ofcertain tin coating Weights applied to strip steel with percentage coldreductions falling within the scope of the .present invention; and

FIGURE 3 is a graphical representation lof the change in thickness ofcertain zinc coating weights applied to strip `steel with percentagecold reductions falling within the scope of the present invention.

FIGURE 4 is a schematic representation of method steps included in theinvention.

Several examples from the above graphical representations follow:

.010 'blackplate reduced 90% will have a thickness of about .001; if theb'lackplate had a coating of 1.5 lbs. of tin per base box, the coatingthickness would be about nine-millionths of an inch (9X10`G); if initialcoating had been a .25 lb. per base box, the coating thickness wouldhave been one and six-tenths millionths of an inch (1.6 104i).

.005 blackplate, when reduced 80%, would have a thickness of .001; ifthe starting coating thickness was 1.5 lbs. of tin per base box, theiinal thickness would be about seventeen and one-half millionths inch(17.5 10 6); it the coating weight initially applied was .5 lb. per basebox,

the iinal thickness would be about six-millionths inch (6 10-6).

The infinite number of variations available can be conceived bycombining the graphical representations of FIGURES 1 and 2 for tin orFIGURES 1 and 3 ier zinc. Other coating metal combinations, dependent onpractical initial coating thickness limits, can be obtained in likemanner. In this regard, while examples from experience with tin, Zinc,`Zinc alloy, aluminum, aluminum alloy, stainless type steel, andtitanium, will predominate in this disclosure, the invention is not solimited. Conventional strip steel inishing operations are concerned withvarious protective coatings for steel; similarly, with the presentinvention. Among the metallic coatings to be considered are thefollowing metals and their alloys-tin, terne, zinc, aluminum, copper,nickel, chromium, cadmium, stainless steel, silver, gold, and titanium.Special consideration will be given to a steel foil plated withstainless type steel. As a practical matter, strip steel can be coatedeconomically with most of the aforementioned metals, without an alloylayer, with coatings up to .001 thick and higher in continuous striplines. For example, referring to FEG- URE 3, .6 ounce per square foot ofZinc has a thickness of labout .001.

As dened, plated steel foil includes gages up to about twoone-thousandths of an inch (.002") made by a cold reduction of coldreduced and annealed strip stock substantially in excess of 50%, withcold reductions ot 97 and higher being contemplated. Therefore, startingmuterial for the present invention can be conventional steel millproduct. Plated strip steel having a thickness of about sixty-vethousandths inch (.065), when reduced approximately 97%, will have agage of about two thousanths of an inch (.002).

Cold reduction can be carried out by cold rolling passes of as low as10% reduction per pass or up to 90% or higher reduction per pass.Certain plated stock, such as tinplate, can take large cold reductionsreadily without any visible effect on the coating or the strip; it isbelieved that the lubricity of tin aids in this respect. Similarexperience has been had with Zinc, aluminum, aluminum alloy, stainlesstype steel coatings and titanium. At thin gages, tinplated steel foiland steel plated with any of the malleable metals included in thisinvention may be reduced two strands at a time by rolling the strandsback to back through the cold reducing mill with conventionalnon-bonding materials such as rolling oils being used between strands.

The amount of cold reduction per pass is largely determined by theeconomics of the process and, to sonic extent, by the desired propertiesof the finished product and the cold reducing properties of thecoatings. The following table will help illustrate why economics entersinto this determination. This table shows the number of passes requiredat various percentages to reduce material having starting gages of .005,.0072, and .0011l to a foil of .0005.

T able I Number of cold rolling passes required to produca .0005 foilPercent Starting gage reduction per pass 2l 25 20 1U l2 l-t 7- 8- t) 4+5 u 3+ /1- 11+ 3- 3 L1- 2 2+ 3- 2- 2- M 1 1+ 2- tot :tl iront thestandard gages of strip steel would require a reduction of substantially70% or higher. If such cold reductions are carried out with less than40% reduction per pass, the number of passes required is high forordinary steel mill practice. Therefore, the aim is to have thereduction per pass exceed 40%; but, consideration must be given to thedesired properties of the foil and the effect of large cold reductionson the coating. Reductions in the range of 40% to 60% per pass arepreferable. Larger cold reductions per pass tend to reduce thespringiness of the foil and special consideration must be given to thecoating which should be either self-annealing or permit a cold reductionin the range -desired without an anneal and should exhibit highmalleability. The large cold reductions and tine gages required toproduce steel foil can be handled well with a cold rolling mill of theSendzimir type. The properties and the pressure and tension controlsavailable on this type of mill are well known in the art so that nofurther description of a Sendzimir mill is necessary to an understandingof the invention.

By making economically feasible reduction of plated steel strip to foilgages, the invention makes possible many new consumer and engineeringuse products. Also, many existing products can be fabricated moreeconomically. Many of the new uses and new products of plated steel infoil gages result from the combination of high tensile strength steelwith the special pr-operties of a coating metal such as copper, cadmium,silver, and the like. Copper plated steel strip, for example, reduced tofoil gages, can be used to form reactance devices, coil windings,capacitors, etc., can be used in plural layers to make pliable shortradius turn conductors, and can be used in other similar uses which takeadvantage of the high electrical conductivity of the surface layercopper and the high tensile strength and excellent handling propertiesof the steel. Silver-plated steel foil can qualify economically for manyspecial electrical uses from which it had previously been barred and,similarly, for cadmium and cadmium alloy plated steel foil.

While aluminum plate-d steel foil also has many electrical applicationsbecause of its good electrical conductivity, it and some of its alloyssuch as aluminum-manganese will be considered with tin and zinc formaking many products where corrosion protection is the most importantfunction of the coating metal. Steel foil, plated with any of thesecoating metals, has numerous uses in packaging, building, decorating,making special textiles, and numerous other industrial applications.These uses are multiplied by the advantages of laminating steel foilwhich will be considered later.

ln packaging, for example, metal plated steel foil from about .0001" toabout .0007 has many of the normal consumer foil uses especially inindustrial wrapping. Metal plated steel foil up to about .001 or .0015"makes excellent foil pouches for freeze-dry products, and the like,where creating a light and Vapor barrier is important. While platedsteel foil of various gages up to about .002 makes excellent semi-rigidpackaging tray structures such as that used for precooked frozen foods,etc., the advantages of all these packaging and other uses over othermetallic foils is the high tensile strength of the steel, its abrasionresistance, and the easy handling properties which permit fabricatingwith much less difiiculty than the other metallic foils. Theseproperties are especially helpful in handling the ne foil gages used forlabel stock.

In the boiling industry, any of the lower cost coating metal foils canbe used for water vapor barrier and insulation purposes moreeconomically than metallic foils currently available. Special corrosionprotection and strength characteristics for many products are availablewith titanium plated steel foil. Honeycomb core and expanded metal aretypical applications for such foil, as well as for foils plated with themore common corrosionresistant metals such as tin, zinc, and aluminum.

Nickel and some of the nickel alloy plated steel foils find specialuses, along with copper and copper alloy plated steel foils, in thedecoration and novelty fields. These and some of the lower-priced metalplated steel foils of the lower thickness gages can also be readily slitinto tine thread providing metallic textile materials of higher strengththan any currently available.

In making products from steel foil, the fabrication may employ folding,die forming, scoring, embossing, and/or a variety of forms of printing.Other uses than those specifically enumerated above will be obvious fromthe present disclosure and are considered to be within the scope of thepresent invention.

Stainless steel plated steel foil can be produced by several methods inaccordance with the teachings of the invention. In this context,stainless steel is used in its broad sense, including what is oftenreferred to in the art as a stainless type steel or merely stainless Assuch, utilization of nickel and/or chromium, or alloys thereof, as analloying agent(s) in sufficient quantities to make steel rust andcorrosion resistant are included. One method is plating mild steel withstainless steel and reducing as previously describe-d. Other methodsinvolve plating -mild steel strip with chromium and/or nickel, or theiralloy; processes for plating nickel, chromium and/or iron are known,e.g. U.S. Patent 2,927,066 and Electroplating Engineering Handbook,Reinhold Publishing Corporation, 1955, pages 176, 177. Heat diffusionapplied to the plated strip or after the plated strip has been reducedto foil gages produces stainless steel plated foil. Methods andapparatus for causing heat diffusion of plated metals are known in theart so that no further description is necessary to an understanding ofthis phase of the invention. However, cold reduction practice within thescope of the present invention has been found to produce stainlessplated steel foil without heat diffusion; for example, mild steelsimultaneously plated with chromium and nickel and then cold reduced tofoil gages produces highly satisfactory stainless plated steel foil.rl`he savings involved in such a process are obvious. Various newindustrial, commercial, and consumer uses of stainless plated steel`foil building structures, such as honeycomb panels, in the packagingindustry for disposable containers, wrappings, laminated and otherwise,have been developed as a result of this new product.

The invention also includes the lamination of steel foil, plated orunplated, with one or more of the following materials: paper,paperboard, Mylar and other well known thermosetting lm materials, heatsealing films commonly referred to as thermoplastic lms, natural andsynthetic textiles, felts, fibers, and filaments, plastic, fiber, andwood sheeting or other metals. The steel foil and lamina are normallyjoined by an adhesive which may be heat or pressure sealed incontinuous-line operations. Steel foil has special advantages over othermetallic foils for laminated products and in manufacture of laminatedproducts because of the high tensile `strength and abrasion resistanceof steel foil.

Through this invention, all the advantages of steel or all theadvantages of steel and a plating metal can be added to the propertiesof other laminating materials making various new products economicallyfeasible. The uses of laminated steel foil extend to all the uses inindustries referred to earlier in relation to non-laminated steel andare expanded by properties and uses for the laminating material itself.

Many of the laminae set forth above may be joined by pressure or heat tothe steel foil, may be spray coated, or may be joined by use ofadhesives. In formulating an adhesive, the mate-rial to be laminated tothe steel foil and the surface character of the foil should beconsidered. Most suitable adhesives can be formulated from basic latexand resin base adhesive inclding epoxy resin compounds, vinyl phenolics,and rubber-base adhesive such as neoprene. The proper formulation cantake care of foil surface oil problems but, in the interest of uniformadherence, the toil surface may be cleaned by cathode cleaning, vaporcleaning, or solvent wipe or rinse. Often merely heating the foil willevaporate the oil and provide uniformity. For example, tinplated foilheated to about 300 F. provided uniform lamination using the adhesivereferred to in the trade as Polybond, a vinyl type copolymer, which isavailable from Polymer Industries, Springdale, Connecticut.

ln disclosing the invention, specific descriptions of several productsand processes were resorted to in the interest of clarity; the scope ofthe invention is not to be limited by such description but is to bedetermined by the appended claims.

What is claimed is:

1. Method for producing metal plated, non-embrittled, steel foilcomprising applying an iron-alloy-layer `free metallic coating to stripsteel, the strip steel having a thickness gage between about .003 andabout .065 and a carbon content up to about .15%, and

cold reducing the metal coated strip steel at least 70%,

without annealing the steel during the cold reducing, by cold rolling toa thickness gage between about .0001 and about .002.

2. The method ot claim 1 in which the coating metal is selected from thegroup consisting of tin, terne, zinc, zinc alloy, aluminum, aluminumalloy, copper, copper alloy, nickel, nickel alloy, chromium, chromiumalloy, cadmium, stainless steel, silver, gold, and titanium.

3. The method of claim 1 in which the cold reduction includes a singlecold rolling pass in which the reduction is about 50%.

4. The method of claim 1 in which the metallic coating applied ismatte-finish tin and in which the cold reducing is carried out on thematte-finish tinplated strip.

5. Method for producing metal plated, non-embrittled, steel foilcomprising applying an iron-alloy-layer free metallic coating to stripsteel, the strip steel having a thickness gage between about .003" andabout .065 and a carbon content up to about .15 the metallic coatinghaving a thickness gage ranging up to about .001, and cold reducing themetal coated strip steel at least 70%, without annealing the steelduring the cold reducing, by cold rolling to a thickness gage betweenabout .0001 and about .002.

6. Method for producing tinplated, non-embrittled, steel foil comprisingelectrolytically applying a matte-finish tinplating to mild steel strip,the thickness gage `of the steel strip being between about .003 andabout .065", the coating weight of the tin ranging up to about 2.0 lbs.per base box, and

cold reducing the matte-finish tinplated steel strip at least 70%without annealing the steel during the cold reducing, by cold rolling toa thickness gage between .0001 and .002.

7. Method for producing non-embrittled steel foil having a stainlesstype steel plating comprising the steps of coating steel strip withstainless type steel metal components including nickel and chromium, thesteel strip having a thickness gage of between about .003 and about .065and a carbon content ranging up to about 0.15%, and

cold reducing the metal coated steel strip at least 70%,

without annealing the steel during the cold reducing, by cold rolling tofoil having a thickness gage between about .0001 and .002.

8. The method of claim 7 further including the step of heating thecoated steel strip before cold reducing to cause diffusion of thestainless type steel metal cornponents into the steel strip.

9. Method for producing stainless type steel coated, non-embrittled,steel foil comprising coating steel strip with stainless type steelmetal components including nickel and chromium, the steel strip having athickness gage of between about .003 and about .065l and a carboncontent ranging up to about 0.15%,

cold reducing the metal coated steel strip at least 70%, withoutannealing the steel during the cold reducing, by cold rolling to foilhaving a thickness gage bctween about .0001 and .002", and then heatingthe cold reduced coated steel strip to cause diffusion of the stainlesstype steel metal components into the steel of the foil.

10. Method for producing stainless type steel plated,

non-embrittled, steel foil comprising plating strip steel simultaneouslywith chromium and nickel, the strip steel having a thickness gagebetween about .003 and about .065" and a carbon content ranging up toabout 0.15%, and

cold reducing the plated strip at least 70%, without annealing the steelduring the cold reducing, by cold rolling to foil having a thicknessgage between about .0001l and .002.

1l. Method for producing a metal plated, nonembrittled, steel foilcomprising applying a plurality of metallic coatings to strip steel, thestrip steel having a (thickness gage between about .003" and about .065and a Carbon content up to about .15%, the coating metals being selectedfrom the group consisting of tin, terne, zinc, aluminum, aluminum alloy,copper, copper alloy, nickel, nickel alloy, chromium, chromium alloy,stainless steel, silver, gold, and titanium, and

cold reducing the metallic coated strip steel at least 70%, withoutannealing the steel during the cold reducing, by cold rolling to athickness gage between .0001 and about .002.

References Cited by the Examiner UNITED STATES PATENTS 1,656,892 1/28Shover 29-528 1,675,134 6/28 Roemer 80-60-7 2,018,522 10/35 Herrmann 2925.3 2,116,107 5/38 Erb 29-18 X 2,316,296 4/43 Simonds 220-72 2,378,4586/45 Avallone 29-528 X 2,384,086 9/45 Glock 204-36 2,573,524 10/51Weisberg 220-72 X 2,576,922 12/51 Camin 29-528 X 2,594,012 4/52 Gritlin220-72 2,731,403 1/56 Rubin 204 28 X 2,762,764 9/56 Owen Ztl-4h282,854,732 10/58 Hessenberg 29-528 2,858,235 10/58 Rex 29-528 2,961,36511/60 Scroog 161-214 2,973,571 3/61 Meyering 29-194 2,998,642 9/61McCawley 29-l94 3,007,854 11/61 Smith 204-*28 3,009,238 11/61 Wesley204-40 3,044,156 7/62 Whitfield 9-194 3,050,825 8/62 Field .2Q-4.513,054,703 9/62 Brasure 161-214 3,057,050 10/62 Hodge 29-528 X 3,064,87411/62 Kaufeld 229-37 X 3,088,624 5/63 Kinghorn 220`72 3,095,361 6/63Stone 20436 3,105,022 9/63 Boggs 204-40 X FOREIGN PATENTS 486,219 6/38Great Britain. 487,844 9/ 36 Great Britain.

New York, 1963, vol. 2, page 134.

RICHARD H. EANES, In., Primary Examiner.

1. METHOD FOR PRODUCING METAL PLATED, NON-EMBRITTLED, STEEL FOILCOMPRISING APPLYING AN IRON-ALLOY-LAYER FREE METALLIC COATING TO STRIPSTEEL, THE STRIP STEEL HAVING A THICKNESS GAGE BETWEEN ABOUT .003" ANDABOUT .065" AND A CARBON CONTENT UP TO ABOUT .15%, AND COLD REDUCING THEMETAL COATED STRIP STEEL AT LEAST 70%, WITHOUT ANNEALING THE STEELDURING THE COLD REDUCING, BY COLD ROLLING TO A THICKNESS GAGE BETWEENABOUT .0001" AND ABOUT .002".